How To Follow Babbage’s Flight

My flight is a single balloon with 2 payloads, each one transmitting “live” images plus telemetry. Another balloonist Anthony Stirk will launch his own flight, from the same site, shortly before mine.

The main payload is called PIE. This has a cutdown mechanism that will release the second payload (TED) at 39km or when it senses a burst. Balloons vary and 39km isn’t guaranteed though there’s a good chance it will be achieved. 39km is of course 31 metres over Felix Baumgartner’s record jump altitude!

Both trackers are model A Pi boards each with UBlox GPS, NTX2 transmitter, Pi Camera module. TED’s camera is where his right eye used to be, and will look outwards for a normal view. PIE’s camera is directly above TED, looking down. So for most of the flight it will mostly see the top of TED’s head.

Flight Plan

Both payloads change what they do with their cameras depending on altitude:

1. Below 2km they take small images (320 x 240)
2. Above 2km they take larger images (512 x 384) and full-res (2592 x 1944) images
3. At 38km (if they get that high) they will take an 8-minute video, to record the release of TED
4. Then, whilst still above 2km, they will take 512 x 384 and 2592 x 1944 images
5. Below 2km they will take an 8-minute video to record the landings
6. After that they will take smaller images again

Because each image takes a few minutes to transmit, and because altitude is only checked every 30 seconds by the imaging script, then those transitions will be delayed. So for example when the flight reaches 39km both payloads will still be transmitting an image taken earlier, and after that finishes they will start sending another one that may also have been taken before the 39km point.

Depending on timings, there may be some periods where no images are transmitted because the camera is taking a video and there are no more images to send, but those should be short. I can’t predict the downtime because it depends on image file sizes and how many packets are still to be sent when the camera switches to video mode.

The full-res images and video are stored only, and not transmitted.

PIE is set to release TED as soon as it detects an altitude of 39000m or greater. This check is done on every new reading from the GPS and triggers a MOSFET-driven resistor cutdown, which should release TED within 2 seconds or so.

Tracking

If you have a suitable radio receiver (one that covers the 70cm band and has USB mode), and you’re within 600km of Berkshire, then please do help track the flight. We do have a lot of receivers these days but with 4 trackers (2 from this flight and 2 from Anthony’s) in the air at the same time, the more we can get the better! If you’ve never tracked a balloon flight before then have a read of this excellent guide. It’s best to get set up before the flight rather than have a panic when it’s up! As well as the receiver you will need the free decoding software dl-fldigi and a simple audio cable to connect the receiver to a PC. Or if you have an Android tablet there’s software for that. Finally, if you don’t have a “real” radio but do have an SDR (Software Defined Radio) dongle, then those work too – see http://ukhas.org.uk/guides:sdr_tracker.

To configure dl-fldigi just choose BABBAGE in the drop-down list, choose TED or PIE (makes no difference as they have the same settings) then hit autoconfigure. Or do it manually: Carrier shift 600Hz, 600 baud, 8 bits, 2 stop bits. Nominal frequencies are 434.075MHz (PIE) and 434.650MHz (TED).

To view the images as they come in, choose View ? SSDV in the menu. You don’t need to do anything else different to normal. You will see the binary image data coming in between telemetry strings, but of course it will just look like garbage. So long as you see the lime-green “Successfully decoded image packet” window then all is good. Telemetry is interlaced with the SSDV packets so you’ll see that coming in too.

Links

Live streams from launch site and chase car: http://www.batc.tv/streams/ukhas and http://www.batc.tv/streams/ukhas2

All SSDV images: http://ssdv.habhub.org (or you can select either payload with http://ssdv.habhub.org/TED or http://ssdv.habhub.org/PIE)